1. Field of the Invention
The present invention relates to a clearance increasing jig of a heat transfer tube that increases a clearance between adjacent heat transfer tubes and an additional installation method of a vibration suppression member using the clearance increasing jig.
2. Description of the Related Art
In the related art, a steam generator having a plurality of heat transfer tubes provided therein was known (see, for example, Patent Literature 1). Each of the heat transfer tubes provided in the steam generator has a U shape and a fluid such as a coolant is circulated in the heat transfer tube. When the fluid is circulated in the heat transfer tube, vibration (fluid excitation vibration) by the circulation of the fluid is generated in a circular arc portion of the U-shaped heat transfer tube. As a result, an anti-vibration bar as an anti-vibration member is inserted into a clearance of the heat transfer tube, serving as the circular arc portion, in the steam generator.
Herein, the anti-vibration bar disclosed in Japanese Patent Application Laid-open No. 61-291896 increases clearances of the plurality of heat transfer tubes. That is, the anti-vibration bar is inserted into the clearance of the heat transfer tubes and thereafter, is brought into contact with the heat transfer tubes by increasing the width of the anti-vibration bar to be slightly wider than the clearance of the heat transfer tubes.
Meanwhile, as the vibration suppression member to be additionally installed, a bar-shaped member may be used. In this case, in order to contact the vibration suppression member with the heat transfer tube, a vibration suppression member having substantially the same thickness as the clearance of the heat transfer tubes may be inserted. However, respective clearances of the heat transfer tubes are not particularly constant due to a size tolerance caused by a variation in flatness level of the heat transfer tube at the circular arc portion. Herein, the flatness level of the heat transfer tube represents a difference between a maximum outer diameter and a minimum outer diameter on one end surface which is orthogonal to a longitudinal direction of the heat transfer tube. As a result, there is a case in which the clearance of the heat transfer tubes is narrower than the thickness of vibration suppression member and in this case, it is difficult to insert the vibration suppression member into the clearance of the heat transfer tubes.